Can body fabrication

ABSTRACT

To produce a cylindrical can body, a cup-shaped workpiece having a relatively thick and relatively short cylindrical wall is telescoped over the end of a mandrel and a rotating ring of hard material is advanced axially onto and along the mandrel to cooperate with the mandrel to thin and spread the cylindrical wall.

ijaite @tatea Patent inventor Ermal C. Frame Dayton, Ohio Appl. No. 806,550

Filed Mar. 12, 1969 Patented July 20, 1971 Assignee Dayton Reliable Tool 8: Mfg. Company Dayton, Ohio CAN BODY FABRECATION 23 Claims, 11 Drawing Figs.

US. Cl i. 72/83, 72/347, 113/120 Int. Cl 321d 22/16 Field of Search 72/347,

Primary Examiner-Richard .l. Herbst Attorney-Smyth, Roston & Pavitt References Cited UNITED STATES PATENTS 10/1932 Fulton 72/348 7/1934 72/77 9/1950 72/124 8/1962 72/85 4/1964 1 13/7 5/1965 72/77 11/1968 72/84 ABSTRACT: To produce a cylindrical can body, a cupshaped workpiece having a relatively thick and relatively short cylindrical wall is telescoped over the end of a mandrel and a rotating ring of hard material is advanced axially onto and along the mandrel to cooperate with the mandrel to thin and spread the cylindrical wall.

CAN BODY FABRICATION BACKGROUND OF THE INVENTION Various fabrication procedures have been employed heretofore for the production of cans of the general type commonly used for beverages and food products. In the conventional fabrication of a tin-coated steel can, for example, a cylindrical shell is first formed out of sheet metal and then a stamped sheet metal bottom is assembled to one end of the shell.

To avoid the necessity of separately fabricating a cylindrical shell and a bottom wall, it is highly desirable to form a can body with an integral bottom wall and such one-piece can bodies made of aluminum alloy have been produced heretofore. One prior art method of producing a one-piece aluminum can body is to use progressive drawing dies .to produce a cupshaped aluminum body of somewhat less than the desired axial dimension and then to place the cup-shaped body on a mandrel for the purpose of ironing" the cylindrical wallof the body by means of a hard metal or carbide ring to thin the cylindrical wall and to elongate the cylindrical wall to the desired axial dimension.

Another prior art method of producing a one-piece aluminum can body employs impact extrusion to produce an intermediate cup-shaped workpiece. It is not practical to'extrude such an intermediate workpiece in .a single-impact stroke because it would be too severe on the dies and because slight defects in the metal and the presence of minute bodies of lubricant would result in too many rejects, and therefore repeated extrusion is employed. The product of the repeated-extrusion is placed on a mandrel and is finished to thedesired final dimension by using a hard metal ring for a simple ironing operation.

All of these prior art techniques result in a can body in which the thickness of the metal isgreater than necessary in some parts of the can and therefore there is a pressing needfor a method of fabricating a one-piece'can body with greater economy of material. This need may be appreciated by setting forth ideal dimensions for a one-piece can body made of an aluminum alloy.

It has been found that the bottom wall of an aluminum alloy I can may be relatively thin and yet be of adequate strength by a liberal margin if the bottom wall is shaped to nonplanar configuration, for example, an inwardly bulged configuration. Thus an aluminum alloy can body of a common size of 2 1 1/16 inch inside diameter may have a shaped bottom wall of a thickness of only 0.0125 inch. It is furtherpossible-to make the cylindrical wall of a can relatively thin in the intermediate region between the ends of the can without reducing the strength of the can below a safe margin. Thusthe cylindrical wall of an aluminum alloy can may abruptly taper in thickness from approximately 0.0125 inch near its bottom end to a minimum thickness of 0.006-00065 inch. It has also been found that if the upper end of such an aluminum alloy can body is necked down to reduced diameter to permit the use.of a top wall of reduced diameter, the neckingdown locally reinforces the cylindrical wall to permit the local thickness of the cylindrical wall to be reduced. Thus,with .the-open end of the aluminum can body strengthened in this manner, the thickness of the cylindrical wall may be of a thickness of only.0.00600-- 0.0065 inch throughout the major intermediate portion of its length with a thickness of approximately 0.0125 near the bottom end and a thickness of 00090-00095 inch near th open end.

If an aluminum alloy can body were fabricated-witbthe above specified thickness dimensions, only 28 to 30 pounds of metal would be required to produce 1,000 can bodies with integral bottom walls. Unfortunately, however, progressive drawing alone, progressive drawing combined with an ironing operation, and repeated extrusion combined with ironing are all inherently incapable of producing such an ideallyndimensioning aluminum alloy can body The aluminum alloy required in each instance is approximately 38 to 40 pounds for 1,000 can bodies with integral bottom walls. Theoretically, then, it is possible to save from 8 to 12 pounds of aluminum alloy per thousand can bodies which means a saving in metal of 15 to 30 percent.

The economic significance of this fact may be appreciated when. it is considered that with aluminum alloy can bodies produced by automatic machinery at rates as high as 600 700 cans per minute, percent of the cost of the cans is in the aluminum alloy, only 20 percent of the cost being labor, overhead and profit. Thus 15 to 30 percent saving in the amount of aluminum alloy means a saving of 16 to 24 percent of the total cost for the can'bodies. At the high rate of production made possible by automatic machinery, a saving of only 5 percent would pile up rapidly and the possibility of obtaining such a saving by some new fabrication technique would warrant investment of a large sum of money in a development program.

The present invention is directed to the problem of providing a fabrication technique for producing one-piece can bodies of highly economical thickness dimensions. The

economical thickness dimensions specified above for aluminum alloy are by way of example only, it being understood that other thickness dimensions would be specified for other metals such as steel and for other materials such as ductile plastics.

SUMMARY QF THE INVENTION By way of example, theinventionis described herein as applied to the production of aluminum alloy can bodies. The fabrication of an aluminum alloy can starts with an aluminum alloy sheet blank having initial nominal thickness substantially in excess of the maximum thickness dimension desired in the cylindrical wall of the finished can body. For example, to produce an aluminum alloy can body with an inside diameter of 2 11/16 inch and with an axial dimension of approximately 4 %inch and with a maximum wall thickness of approximately 0.0125 inch, the initial thickness of the sheet metal bland may be approximately 0.0200.025 inch.

The first step is to form the sheet metal blank to an intermediate configuration of a cup of approximately the desired final inside diameter and of an axial dimension substantially less than the final axial dimension of the can body. For example, the axial dimension of the cylindrical wall of the cup may be approximately 2 -%inch which is approximately 60 percent of the desired final axial dimension.

Preferablythe bottom wall of the cup-shaped receptacle is of reduced thickness, say a thickness of approximately 0.0125 inch, and for this purpose the bottom wall of the cup-shaped receptacle may be subjected to a suitable impact operation or pressure operation to squeeze the material and thus cause a portion of the material of the bottom wall to flow radially outward. and form an outer circumferential bead.

The next step is to telescope the cup-shaped receptacle over a nonrotating mandrel in a fixed manner and to spread the metal of the circumferential wall including the metal of the circumferential bead.-For this purpose, a ring of hard material is rotated on its axis and at the same time is advanced coaxially of the mandrel to telescope over the mandrel and to advance lengthwise of the mandrel. With the inside diameter of the rotating ring equal to the desired outside diameter of the final can body, the advancing rotating ring displaces surplus metal of the cylindrical wall of the receptacle axially and thus not only thins the cylindrical wall to the desired length. Such a metal ring may, for example, have a working surface of tungsten carbide.

1 In the presently preferred embodiment of the apparatus for carrying out the invention, --.the rotary processing 'ring is suitably journaled on acarriage and a motorfor rotating the ring is-also mounted on the'carriage. With the rotating ring positioned coaxially of the mandrel and retracted from the end of the mandrel, suitable means is employed to advance the carriage and thus advance the rotating ring axially to the extent required to finish the cylindrical wall of the workpiece.

The preferred practice of the invention is characterized by the employment of a mandrel that varies in diameter along its length to vary the thickness of the cylindrical wall to save material without unduly weakening the cylindrical wall. In the presently preferred practice of the invention the mandrel coo erates with the rotary ring to cause the cylindrical wall of the can body to be relatively thin in its midregion.

The features and advantages of the invention may be understood from the following detailed description andlhc accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which are to be regarded as merely illustra tive:

FIG 1 is a perspective view of the presently preferred ap paratus for processing what may be termed a second intermediate cup-shaped receptacle;

FIG. 2 is a longitudinal cross section of a portion of FIG. 1 showing the relation of the rotary ring to the mandrel at the start of the processing of the second intermediate cup-shaped receptacle;

FIG. 3 is a fragmentary section-taken along the line 3-3 of FIG. 2 showing how a tungsten carbide liner for the ring may be keyed to the ring;

FIG. 4 is a sectional view showing how a first intermediate cup-shaped receptacle may be placed on a lower of two dies for the purpose of shaping and simultaneously thinning the bottom wall of the receptacle to produce the second intermediate cup-shaped receptacle;

FIG. 5 is a similar view showing how the two dies close to thin the bottom wall of the receptacle to displace surplus metal radially to produce the second intermediate cup-shaped receptacle;

FIG. 6 is an enlarged sectional view showing how the advancing rotary ring thins the cylindrical wall of the second intermediate cup-shaped receptacle;

FIG. 7 is a view similar to FIG. 6 showing how the inner circumference of the ring may be shaped to thin the circumferential wall of the second intermediate receptacle in two stages;

FIG. 8 is a similar view showing how the ring may be shaped to thin the wall of the second intermediate receptacle in three stages;

FIG. 9 shows how the apparatus may be modified to employ spring pressure to keep the cup-shaped receptacle from rotating relative to the mandrel on which it is mounted;

FIG. 10 is an enlarged longitudinal sectional view of the mandrel showing how the rotary ring processes a can body; and

FIG. 11 is a longitudinal sectional view showing how the resulting can body may be flanged and at the same time reduced in diameter in a well-known manner to receive a can top of reduced diameter.

DESCRIPTION OF THE PREFERRED PRACTICE OF THE INVENTION FIG. 11 shows a preferred configuration of a can body that is the end result of the process taught by the invention. It is to be noted that the can body is necked down to a reduced diameter near its open end to permit the can body to be closed by a can end of reduced diameter, this configuration strengthening the can body near its open end to permit the corresponding portion of the circumferential Wall to be reduced in thickness. It is contemplated that the can body shown in FIG. 11 will at least approximate most of the ideal thickness dimensions heretofore set forth. Thus, the bottom wall of the can body may have a thickness of approximately 0.0125 inch; the cylindrical wall of the can body may be of the same thickness of 0.0125 inch near the bottom end and may be of a thickness of approximately 0.0090-00095 inch near the open end of the can body, the intermediate major portion of the length of the cylindrical wall being of 0.00600.0065 inch in thickness.

Since the employment of a ring to process the cylindrical wall of a cup-shaped workpiece results in a cylindrical wall of uniform outside diameter, the desired variation of the wall thickness may be accomplished by varying the outside diameter of the mandrel. Accordingly, the mandrel that cooperates .with the ring varies in diameter along its length inversely with the desired variations in the thickness of the cylindrical wall of the finished can body.

In accordance with this concept, in FIG. 10 the radial dimension of the portion of the mandrel 20 near its outer end is smaller than the inside radius of the rotary ring by a difference of 0.0125 inch to cause this portion of the cylindrical wall of the can body to be of this thickness. At the base end of the mandrel the difference is 0.009-0.0095 inch. The major portion of the length of the mandrel between these two extremes is of a radius that is smaller than the inside diameter of the rotary ring by a difference of only 0.006--0.0065 inch.

Referring again to FIG. 10, preferably a suitable stripper 22 is provided at the base end of the mandrel. The inner circumference of the stripper 22 is formed with an annular recess 24 to engage the rim of the can body at the end of the thinning operation.

It is further preferred that the stripping of a semifinished can body from the mandrel 20 at the end of the wall-thinning operation be facilitated by a burst of compressed air. For this purpose the mandrel 20 is provided with an axial air passage 25 which has a reduced end portion 26 and the concave end of the mandrel is formed with radial grooves 28 to provide radial distribution of the compressed air. The compressed air in combination with the stripper 22 is highly effective to overcome the resistance to removal of the can body that arises from the fact that the mandrel 20 is of maximum diameter in its mid region, it being necessary for the metal of the circumferential wall of the can body near its open end to stretch circumferentially slightly to pass over the mid region of the mandrel.

Blank sheet stock employed to fabricate the can body may have a thickness of 0.020-0.025 inch and is first processed by suitable drawing dies (not shown) to produce what may be termed a preliminary cup-shaped receptacle, generally designated 32 in FIG. 4, which has a cylindrical wall of substantially the starting thickness of 0.020-0.025 inch and which has a flat bottom wall of substantially the same thickness. The cylindrical wall 36 is slightly flared to conform to the taper of the leading end of the mandrel 20. FIGS. 4 and 5 illustrate the operation by means of which the preliminary cup-shaped receptacle 32 is converted into what may be termed an intermediate cup-shaped receptacle 34 having a shaped bottom wall 35 and a cylindrical wall 36.

In FIG. 4 the preliminary cup-shaped receptacle 32 is telescoped over a lower die 37 which cooperates with an upper die 38. The upper end of the lower die 37 is concave to conform to the desired shape of the bottom wall of the finished can body and the upper die 38 has a lower end of complementary configuration. The two dies 37 and 38 cooperate to thin the bottom wall by a squeezing operation and preferably the two dies close together with relatively highimpact force. The surplus metal of the bottom wall is extruded radially in all directions to result in the formation an outer circumferential bead. Thus, when the two dies 37 and 38 close together to thin the bottom wall of the primary receptacle 32 to a thickness of approximately 0.0125 inch, the intermediate cup-shaped receptacle 34 is formed and has an outer circumferential bead 40.

FIG. 2 shows how in preparation for the metal-thinning operation, by a rotary ring the intermediate cup-shaped receptacle 34 is telescoped over the leading end of the mandrel 20. The intermediate cup'shaped receptacle 34 is of approximately the inside diameter of the desired can body but is only somewhat more than half as long. In this example, the intermediate cuprshaped receptacle 34 has an inside diameter of approximately 2 ll/l'6 inches and has an axial dimension of approximately 2 36 inches which is approximately 58 percent of the desired axial dimension of 4 if; inches of the final can body. Thus, the cylindrical wall of the intermediate cupshaped receptacle 34 is to be increased in axial dimension by approximately 73; percent to produce the desired end product. If a cylindrical wall of any given thickness if lengthened by 73 percent, its thickness is reduced to 58 percent of its starting thickness. Thus the reduction in thickness is 42 percent and the starting thickness is 73 percent greater than the final thickness.

The preferred embodiment of the apparatus for carrying out the method taught by the invention is illustrated by FIGS. l 3 wherein the moving parts of the apparatus are mounted on a base 42 which is provided with a control panel 44 having pushbuttons 45 for electrical and hydraulic control of the operation. Mounted on the base 42 is a fixed upright block 48 in which the previously mentioned mandrel 20 is slidingly mounted in a fixed sleeve 48. The mandrel 20 is moved axially by a hydraulic power cylinder 50 under the control of a suitable four-way valve (not. shown) and is prevented from rotation by a spline (not shown) which extends radially inward from the sleeve 48 into a longitudinal groove 52 of the mandrel.

The base 42 further carries a pair of guide rails 54 on which is slidingly mounted a suitable carriage that carries the required rotary ring 55 which is shown in cross section in FIG. 2. The carriage includes a housing 56 in which the rotary ring 55 isjoumaied and further includes a U-shaped yoke 58 with a pedestal 60 extending upward from the yoke to support. a motor 62 for actuating the rotary ring. The motor carries a drive shaft 64 on which is mounted a drive pulley 65 that actuates the rotary ring by means of a pair of V-belts 66, the V- belts extending through windows 68 in the housing 56. Reciprocation of the carriage on the guide rails 54 is accomplished by a hydraulic power cylinder 70 having a piston rod 72 connected to the yoke 58.

Also mounted on the base 42 is a fixed upright block 74 which fixedly carries a horizontally extending shank 75, which, asbest shown in FIG. 2, terminates in a pressure head 76. When the intermediate cup-shaped receptacle 36 is mounted on the mandrel 20 in the manner shown in FIG. 2 and the hydraulic power cylinder 50 is activated, the power cylinder presses the leading end of the mandrel towards the pressure head 76 and thereby clamps the intermediate cupshaped receptacle against rotation on the mandrel 20.

The rotary ring 55 may be joumaled in the housing 56 in any suitable manner. In the construction shown, the rotary ring 55, which may be made of steel, is joumaled between two bronze bearing rings 78 and 80 and for this purpose the steel ring has opposite cylindrical flanges 82 that extend into corresponding circular grooves 84 in the two bearing rings. The bearing ring 78 fits into an annular seat 85 in the housing 56 and the bearing ring 80 is releasably mounted on the housing by suitable screws 86. The periphery of the rotary ring 55 is formed with a pair of circumferential grooves as shown for engagement by the two V-belts 66.

In the preferred embodiment of the invention, the rotary ring 55 has an inner circumferential liner that spreads the metal of the cylindrical wall of the cup shaped member 30 and for this purpose the liner may be made of any suitable hard material such as tungsten carbide. The liner 90 may be removably mounted inside the rotary ring 55 in any suitable manner. In the construction shown in FIG. 2 one end of the liner 90 abuts a radial shoulder 92 of the rotary ring 55, the liner being confined between the shoulder 92 and a snap ring 94. To prevent relative rotation between the linerv 90 and the rotary ring 55, the liner may be formed with one or more longitudinal ribs 95 as indicated in FIG. 3, that fit into corresponding longitudinal grooves 96 in the rotary ring.

The manner in which the apparatus functions for its purpose may be understood from the foregoing description. With the mandrel 20 axially retracted by the hydraulic power cylinder 50, an intermediate cup-shaped receptacle 34 is telescoped onto the leading end of the mandrel and then the hydraulic power cylinder is activated to thrust the mandrel towards the pressure head 76 to clamp the cup-shaped receptacle between the mandrel and the pressure head and thus effectively anchor the cup-shaped receptacle against rotation relative to the mandrel. At this point in the operation, the parts are positioned as shown in FIGS. 1 and 2, the carriage being retracted to retract the rotary ring from the leading end of the mandrel 20.

With the ring 55 rotated at a suitable speed by the motor 62, for example 570 r.p.m., hydraulic power cylinder 70 is activated to advance the carriage and thereby advance the rotating ring axially onto and over the cup-shaped receptacle 34 on the mandrel 20. FIG. 6 indicates how the advancing rotating liner 90 displaces metal of thecylindrical wall 36 of the cupshaped receptacle 34 to thin the cylindrical wall. Preferably the liner 90 has a smoothly curved inner rim 98 on its leading end which acts on the metal in the manner indicated, the rotating liner displacing a bead 100 of surplus metal as it advances and thins the cylindrical wall 36 of the cup-shaped member 34.

At the end of the axial advance of the rotary ring 55 the cylindrical wall 36 of the cup-shaped member 34 is thinned to the desired degree and at the same time the cylindrical wall is extended to the length desired for the can body. The carriage is then retracted to retract the rotary ring 55 from the finished can body and then a suitable cutting means is advanced to the can body on the mandrel 20 to penetrate the cylindrical wall of the can body. The cutting means is then rotated as indicated by the arrow 126 to trim the can body to the desired length, the trimming operation leaving a ring of sheet metal on the mandrel. The hydraulic power cylinder 50 is then activated to retract the mandrel 20 from the pressure head 76 thereby to terminate the clamping of the can body to the mandrel. The final retraction movement of the mandrel brings the severed ring of sheet metal against the stripper 22 and simultaneously a burst of compressed air is delivered to the air passage 25 to dislodge the can body from the mandrel, The can body and the severed ring of sheet material drop through an opening 128 in the base 42. Thereafter the can body is both necked down and flanged by suitable dies to result in the final product shown in FIG. 11.

The present process has a number of advantages over a conventional ironing operation wherein a hard metal ring cooperates with a mandrel to thin a cylindrical wall without rotation of the ring. In the first place, if the ironing ring is not floatingly supported with a certain freedom for lateral movement, the metal may pile up excessively at one point of the ring to result in rupture of the workpiece and, on the other hand, if the ironing ring is floatingly supported, localized resistance, for example a local thick spot in the metal, causes the mandrel and/or ring to shift laterally to result in a nonuniform cylindrical wall. In contrast the rotating ring of the present invention instead of merely pushing the surplus metal axially of the mandrel by brute force acts on the metal helically with a circumferential component of motion that tends to spread a thick spot laterally to eliminate the thick spot. Because of the ease with which the rotating ring overcomes thick spots without tearing the metal, the rotating ring may be closely controlled to conform accurately to a straight axis for close control of the thickness of the finished cylindrical wall and therefore the finished cylindrical wall may be made as thin as desired.

Another disadvantage of ironing the metal with a nonrotating ring is that a minor defect such as a crack in the sheet metal usually results in a reject whereas the circumferential component of motion of a rotating ring actually tends to heal defects in the material of the cylindrical wall.

It is to be further noted that the rate of movement of a nonrotating ironing ring relative to the cylindrical wall of a workpiece is limited to the rate of axial movement of the ring whereas the rate of movement of the working surface of a rotating ring relative to the cylindrical wall of a workpiece depends on the helix angle of the relative motion. If the ratio between the circumferential speed of the inner periphery of the rotating ring relative to the speed of axial travel is only lzl the motion of the inner surface of the ring relative to the work piece is only approximately 40 percent greater than the rate of axial travel of the ring, but if the ring rotates at a relatively high speed and is moved axially at a relatively slow speed, the motion of the inner circumferential surface of the ring relative to the workpiece approaches the circumferential speed of the inner surface of the ring and is a great many times more than the axial speed of the ring. A special advantage of such a high relative speed is the great amount of heat generated by friction to soften the displaced metal and thus facilitate displacement flow of the metal to reduce the resistance to axial movement of the ring.

Since the described liner 9 is of uniform-inside diameter, it reduces the thickness of the cylindrical wall 32 of the cupshaped receptacle 30 in a single stage. FIG. 7 shows how a liner 90a and a separate abutting liner 90b may be employed to thin the cylindrical wall 32 in two stages. The liner 90a has the usual rounded inner rim 98a on its leading end and the end portion 102 of the liner immediately behind the rounded rim is of a diameter to only partially reduce the thickness of the cylinder 32 to the desired ultimate thickness. The end portion 92 of the liner terminates at a sloping shoulder 104 which provides a smooth transition to the remaining portion 105 of the liner which completes the thinning of the cylindrical wall to the desired degree. Thus the first stage of reduction in thickness of the cylindrical wall 32 is carried out by the leading rounded rim 98a and the adjacent leading end portion 102 of the liner while the second stage is carried out by the sloping shoulder 104 and the adjacent remaining portion 105 of the liner.

FIG. 8 shows a set of abutting liners 90c, 90d and 90g which reduce the thickness of the cylindrical wall 32 of the workpiece in three stages. The first stage in reduction of thickness is carried out by the rounded inner rim 98b and an adjacent end portion 106 of the liner 900; the second stage is carried out by a sloping shoulder 108 and an adjacent portion 1 10 of the same liner 90c; and finally, the third stage is carried out by a sloping shoulder l 12 of the liner 90dand the remaining portion 1 14 of the liner 90d.

ln the described apparatus, the clamping pressure between the pressure head 76 and the mandrel that immobilizes a cup-shaped workpiece on the mandrel is created solely by the hydraulic power cylinder 50. H6. 9 shows how the clamping pressure may be determined solely by a coil spring 115. In FIG. 9 the pressure head 76a is mounted on a stem [16 that telescopes into the tubular end of a shank 75a that fixedly extends from the previously mentioned rigid block 74. In the construction shown, the stem 116 of the pressure head is keyed against rotation and is surrounded by a sleeve 118 that is secured by radial screws 120. An enlargement 122 on the inner end of the stem 116 cooperates with the inner end of the sleeve 118 to limit axial outward movement of the pressure head 76a.

In this modification of the invention the hydraulic power cylinder 50 advances the leading end of the mandrel 20 to a limit position which is indicated by the dotted line 124 in FIG. 9. At this predetermined limit of advance of the mandrel, the coil spring 115 is compressed to a predetermined extent to provide a predetermined force for clamping the cup-shaped workpiece against rotation relative to the mandrel 20.

My description in specific detail of the selected process of the invention will suggest various changes, substitutions and other departures from my disclosure.

lclaim:

l. A method of fabricating from ductile sheet material a cylindrical can body with an integral bottom wall, characterized by the steps of:

forming the ductilesheet material into a cup-shaped receptacle having a cylindrical wall of substantially the desired inside diameter of the can body and having an axial dimension substantially less than the desired axial dimension of the can body with the cylindrical wall of the receptacle substantially thicker than the thickness desired in the finished can body; telescoping the cup-shaped receptacle over the end of a mandrel having a cross section corresponding to the desired internal configuration of the finished can body;

providing a hard ring of an inside diameter exceeding the outside diameter of the mandrel by substantially twice the thickness desired for the cylindrical wall of the finished can body; and

advancing the ring axially over the mandrel from the end thereof. while simultaneously causing relative coaxial rotation between the ring and the mandrel to cause the inner circumferential surface of the ring to advance helically of the mandrel to thin the cylindrical wall of the receptacle to thedesired final thickness and to spread the material of the cylindrical wall to increase the axial dimension of the receptacle to at least the desired final axial dimension of the can body.

2. A method of fabricating from ductile sheet material a cylindrical can body with an integral bottom wall, characterized by the steps of:

forming the ductile sheet material into a cup-shaped receptacle having a cylindrical wall of substantially the desired inside diameter of the can body and having an axial dimension substantially less than 75 percent of the desired axial dimension of the can body with the average thickness of the cylindrical wall of the receptacle at least 35 percent thicker than the average thickness desired in the finished can body;

telescoping the cup-shaped receptacle over the end of a mandrel having a cross section corresponding to the desired internal configuration of the finished can body;

providing a hardring of an inside diameter exceeding the outside diameter of the mandrel by substantially twice the thickness desired for the cylindrical wall of the finished can body; and

advancing the ring axially over the telescoped receptacle from the bottom end thereof while simultaneously causing relative coaxial rotation between the ring and the mandrel to cause the inner circumferential surface of the ring to advance helically of the mandrel to thin the cylindrical wall of the receptacle to the desired final thickness and to spread the material of the cylindrical wall to increase the axial dimension of the receptacle to at least the desired final axial dimension of the can body.

3. A method as set forth in claim 1 which includes the step of pressing the bottom wall of the receptacle against the end of the mandrel to anchor the receptacle against rotation relative to the mandrel.

4. A method as set forth in claim 1 in which the mandrel is held against rotation and the ring is rotated as it is advanced.

5. A method of fabricating from ductile sheet material a cylindrical can body with an integral bottom wall, characterized by the steps of:

providing a blank of ductile sheet material of a thickness greater than any wall thickness desired in the finished can y;

forming the blank sheet into a cup-shaped receptacle having a cylindrical wall of substantially the desired inside diameter of the can body and having an axial dimension substantially less than the desired axial dimension of the can body with the cylindrical wall of the receptacle substantially thicker than the thickness desired in the finished can body;

squeezing the bottom wall of the cup-shaped receptacle to 7 reduce the thickness of the bottom wall to the desired final thickness and to spread material of the bottom wall radially to form a circumferential bead on the receptacle;

telescoping the cup-shaped receptacle over the end of a mandrel having a cross section corresponding to the desired internal configuration of the finished can body;

providing a hard ring of an inside diameter exceeding the outside diameter of the mandrel by substantially twice the thickness desired for the cylindrical wall of the finished can body; and

advancing the ring axially over the telescoped receptacle from the bottom end thereof while simultaneously causing relative coaxial rotation between the ring and the mandrel to cause the inner circumferential surface of the ring to advance helically of the mandrel to thin the cylindrical wall of the receptacle to the desired final thickness and to spread the material of the cylindrical wall including said bead to increase the axial dimension of the receptacle to at least the desired final axial dimension of the can body.

6. A method as set forth in claim 1 in which the leading inner circumferential rim of the ring is of rounded cross-sectional configuration.

7. A method as set forth in claim 1 in which the inner circumference of the ring is of stepped configuration to thin the cylindrical wall of the receptacle by stages.

8. A method as set forth in claim 1 in which the inside diameter of the leading end portion of the ring is less than the outside diameter of the receptacle but greater than the desired outsidediameter of the finished can body; and

in which the ring is formed with an inner circumferential shoulder spaced from the leading end portion of the ring, the inside diameter of the ring being stepped down at the shoulder to substantially the desired outside diameter of the finished can body.

9. A method as set forth in claim 1 in which the inside diameter of the leading end portion of the ring is less than the outside diameter of the receptacle but greater than the desired outside diameter of the finished can body; and

in which the ring is formed with a plurality of inner circumferential shoulders at each of which the inside diameter of the ring steps down, the last shoulder stepping the inside diameter down to the desired outside diameter of the finished can body.

10. A method as set forth in claim I in which the mandrel tapers in diameter towards its opposite ends for maximum thinning of the material in the intermediate region of the length of the cylindrical wall of the finished can body.

11. A method as set forth in claim 1 which includes the step of trimming the cylindrical wall of the receptacle to length while the receptacle is on the mandrel after the receptacle is processed by the ring.

12. An apparatus for spreading the material of the cylindrical wall of a cup-shaped receptacle for the dual purpose of thinning the cylindrical wall to a predetermined thickness and of increasing the axial dimension of the cylindrical wall, comprising:

a mandrel dimensioned to fit into the receptacle to support the receptacle from inside, said mandrel tapering in diameter towards its opposite ends for maximum thinning of the material in the intermediate region of the length of the cylindrical wall of the fi hi ied can body;

a ring having an inner circumferential surface of material substantially harder than the material of the receptacle and having an inside diameter exceeding the diameter of the mandrel by substantially twice said predetermined thickness;

means to create relative axial movement between the ring and the mandrel to advance the ring coaxially of the mandrel over the end of the mandrel and along the length of the mandrel; and

means to cause relative coaxial rotation between the ring and the mandrel as the mandrel advances.

13. An apparatus as set forth in claim 12 which includes means to hold the receptacle against rotation relative to the mandrel.

14. An apparatus as set forth in claim 12 which includes means to press the bottom wall of the receptacle against the end of the mandrel to anchor the receptacle against rotation relative to the mandrel.

15. An apparatus as set forth in claim 12 which includes:

a carriage on which the ring is rotatably mounted;

means on the carriage to rotate the ring; and

means to shift the carriage axially of the mandrel.

16. An apparatus as set forth in claim 12 in which the inner rim of the leading end of the ring is of rounded cross-sectional configuration.

17. An apparatus as set forth in claim 12 in which the inner circumference of the ring is of stepped configuration to thin the cylindrical wall of the receptacle by stages.

18. An apparatus as set forth in claim 12 in which the inside diameter of the leading end portion of the ring is less than the outside diameter of the receptacle but greater than the desired outside diameter of the finished can body; and

in which the ring is formed with an inner circumferential shoulder spaced from the leading end of the ring, the inside diameter of the ring being stepped down at the shoulder to substantially the desired outside diameter of the finished can body.

19. An apparatus as set forth in claim 12 in which the inside diameter of the leading end portion of the ring is less than the outside diameter of the receptacle but greater than the desired outside diameter of the finished can body; and

in which the ring is formed with a plurality of inner circumferential shoulders at each of which the inside diameter of the ring steps down, the last shoulder stepping the inside diameter down to the desired outside diameter of the finished can body.

20. An apparatus as set forth in claim 12 in which said ring has a replaceable liner of tungsten carbide providing said inner circumferential surface of the ring.

21. An apparatus as set forth in claim 12 which includes means to trim the thinned cylindrical wall of the receptacle to length while the receptacle is on the mandrel.

22. An apparatus as set forth in claim 12 in which the ring has at least one replaceable liner.

23. An apparatus as set forth in claim 22 in which the ring has a plurality of liners positioned end to end. 

1. A method of fabricating from ductile sheet material a cylindrical can body with an integral bottom wall, characterized by the steps of: forming the ductile sheet material into a cup-shaped receptacle having a cylindrical wall of substantially the desired inside diameter of the can body and having an axial dimension substantially less than the desired axial dimension of the can body with the cylindrical wall of the receptacle substantially thicker than the thickness desired in the finished can body; telescoping the cup-shaped receptacle over the end of a mandrel having a cross section corresponding to the desired internal configuration of the finished can body; providing a hard ring of an inside diameter exceeding the outside diameter of the mandrel by substantially twice the thickness desired for the cylindrical wall of the finished can body; and advancing the ring axially over the mandrel from the end thereof while simultaneously causing relative coaxial rotation between the ring and the mandrel to cause the inner circumferential surface of the ring to advance helically of the mandrel to thin the cylindrical wall of the receptacle to the desired final thickness and to spread the material of the cylindrical wall to increase the axial dimension of the receptacle to at least the desired final axial dimension of the can body.
 2. A method of fabricating from ductile sheet material a cylindrical can body with an integral bottom wall, characterized by the steps of: forming the ductile sheet material into a cup-shaped receptacle having a cylindrical wall of substantially the desired inside diameter of the can body and having an axial dimension substantially less than 75 percent of the desired axial dimension of the can body with the average thickness of the cylindrical wall of the receptacle at least 35 percent thicker than the average thickness desired in the finished can body; telescoping the cup-shaped receptacle over the end of a mandrel having a cross section corresponding to the desired internal configuration of the finished can body; providing a hard ring of an inside diameter exceeding the outside diameter of the mandrel by substantially twice the thickness desired for the cylindrical wall of the finished can body; and advancing the ring aXially over the telescoped receptacle from the bottom end thereof while simultaneously causing relative coaxial rotation between the ring and the mandrel to cause the inner circumferential surface of the ring to advance helically of the mandrel to thin the cylindrical wall of the receptacle to the desired final thickness and to spread the material of the cylindrical wall to increase the axial dimension of the receptacle to at least the desired final axial dimension of the can body.
 3. A method as set forth in claim 1 which includes the step of pressing the bottom wall of the receptacle against the end of the mandrel to anchor the receptacle against rotation relative to the mandrel.
 4. A method as set forth in claim 1 in which the mandrel is held against rotation and the ring is rotated as it is advanced.
 5. A method of fabricating from ductile sheet material a cylindrical can body with an integral bottom wall, characterized by the steps of: providing a blank of ductile sheet material of a thickness greater than any wall thickness desired in the finished can body; forming the blank sheet into a cup-shaped receptacle having a cylindrical wall of substantially the desired inside diameter of the can body and having an axial dimension substantially less than the desired axial dimension of the can body with the cylindrical wall of the receptacle substantially thicker than the thickness desired in the finished can body; squeezing the bottom wall of the cup-shaped receptacle to reduce the thickness of the bottom wall to the desired final thickness and to spread material of the bottom wall radially to form a circumferential bead on the receptacle; telescoping the cup-shaped receptacle over the end of a mandrel having a cross section corresponding to the desired internal configuration of the finished can body; providing a hard ring of an inside diameter exceeding the outside diameter of the mandrel by substantially twice the thickness desired for the cylindrical wall of the finished can body; and advancing the ring axially over the telescoped receptacle from the bottom end thereof while simultaneously causing relative coaxial rotation between the ring and the mandrel to cause the inner circumferential surface of the ring to advance helically of the mandrel to thin the cylindrical wall of the receptacle to the desired final thickness and to spread the material of the cylindrical wall including said bead to increase the axial dimension of the receptacle to at least the desired final axial dimension of the can body.
 6. A method as set forth in claim 1 in which the leading inner circumferential rim of the ring is of rounded cross-sectional configuration.
 7. A method as set forth in claim 1 in which the inner circumference of the ring is of stepped configuration to thin the cylindrical wall of the receptacle by stages.
 8. A method as set forth in claim 1 in which the inside diameter of the leading end portion of the ring is less than the outside diameter of the receptacle but greater than the desired outside diameter of the finished can body; and in which the ring is formed with an inner circumferential shoulder spaced from the leading end portion of the ring, the inside diameter of the ring being stepped down at the shoulder to substantially the desired outside diameter of the finished can body.
 9. A method as set forth in claim 1 in which the inside diameter of the leading end portion of the ring is less than the outside diameter of the receptacle but greater than the desired outside diameter of the finished can body; and in which the ring is formed with a plurality of inner circumferential shoulders at each of which the inside diameter of the ring steps down, the last shoulder stepping the inside diameter down to the desired outside diameter of the finished can body.
 10. A method as set forth in claim 1 in which the mandrel tapers in diameter towards its opposite ends for maximum thinning of the material in the interMediate region of the length of the cylindrical wall of the finished can body.
 11. A method as set forth in claim 1 which includes the step of trimming the cylindrical wall of the receptacle to length while the receptacle is on the mandrel after the receptacle is processed by the ring.
 12. An apparatus for spreading the material of the cylindrical wall of a cup-shaped receptacle for the dual purpose of thinning the cylindrical wall to a predetermined thickness and of increasing the axial dimension of the cylindrical wall, comprising: a mandrel dimensioned to fit into the receptacle to support the receptacle from inside, said mandrel tapering in diameter towards its opposite ends for maximum thinning of the material in the intermediate region of the length of the cylindrical wall of the finished can body; a ring having an inner circumferential surface of material substantially harder than the material of the receptacle and having an inside diameter exceeding the diameter of the mandrel by substantially twice said predetermined thickness; means to create relative axial movement between the ring and the mandrel to advance the ring coaxially of the mandrel over the end of the mandrel and along the length of the mandrel; and means to cause relative coaxial rotation between the ring and the mandrel as the mandrel advances.
 13. An apparatus as set forth in claim 12 which includes means to hold the receptacle against rotation relative to the mandrel.
 14. An apparatus as set forth in claim 12 which includes means to press the bottom wall of the receptacle against the end of the mandrel to anchor the receptacle against rotation relative to the mandrel.
 15. An apparatus as set forth in claim 12 which includes: a carriage on which the ring is rotatably mounted; means on the carriage to rotate the ring; and means to shift the carriage axially of the mandrel.
 16. An apparatus as set forth in claim 12 in which the inner rim of the leading end of the ring is of rounded cross-sectional configuration.
 17. An apparatus as set forth in claim 12 in which the inner circumference of the ring is of stepped configuration to thin the cylindrical wall of the receptacle by stages.
 18. An apparatus as set forth in claim 12 in which the inside diameter of the leading end portion of the ring is less than the outside diameter of the receptacle but greater than the desired outside diameter of the finished can body; and in which the ring is formed with an inner circumferential shoulder spaced from the leading end of the ring, the inside diameter of the ring being stepped down at the shoulder to substantially the desired outside diameter of the finished can body.
 19. An apparatus as set forth in claim 12 in which the inside diameter of the leading end portion of the ring is less than the outside diameter of the receptacle but greater than the desired outside diameter of the finished can body; and in which the ring is formed with a plurality of inner circumferential shoulders at each of which the inside diameter of the ring steps down, the last shoulder stepping the inside diameter down to the desired outside diameter of the finished can body.
 20. An apparatus as set forth in claim 12 in which said ring has a replaceable liner of tungsten carbide providing said inner circumferential surface of the ring.
 21. An apparatus as set forth in claim 12 which includes means to trim the thinned cylindrical wall of the receptacle to length while the receptacle is on the mandrel.
 22. An apparatus as set forth in claim 12 in which the ring has at least one replaceable liner.
 23. An apparatus as set forth in claim 22 in which the ring has a plurality of liners positioned end to end. 